(a) Field of the Invention
The present invention relates to an expansion mechanism for minimally invasive lumbar operation, and particularly to an expansion mechanism for minimally invasive lumbar operation which protects nerve tissues in operations and makes small incisions.
(b) Description of the Prior Art
Lumbar deteriorations, such as vertebra stenosis, herniated disc etc., often lead to serious sciatica, claudication or nerve degeneration. Some of the patients have to be treated surgically, but always hesitate to be further treated surgically after long-term restoration and recurrence. In a traditional operation, as shown in FIGS. 1 and 2, fascia and supraspinous ligament is cut along a middle of a patient's back. Muscles 41 surrounding a vertebra 4 are poked along a periosteum by a tool 42, and are anchored at opposing sides by a hook 43. Ligament adhered to the vertebra 4 have to be ruled out. A traditional surgery laminectomy needs to remove spines and interspinous ligament to abirrate nerves. This process may damage partial vertebra, muscles, and spines. In general, this process has following deficiencies:
1. Even if the muscles have been sutured, the muscles and the spines can not recover as they should be originally and are inconsistent with physical back muscles.
2. dead space is excessively large, taking a risk of epidural fibrosis thereby influencing treatment effect.
3. supraspinous ligament, spines and interspinous ligament are removed, tending to make the spinal column instable.
The traditional operation has much shortcomings, and correspondingly, a minimally invasive operation which makes small incisions and damages minimum tissues is advanced. Currently, such a minimally invasive operation is normally called endoscopic treatment, as shown in FIG. 3. In the endoscopic treatment, a sleeve 5 with a diameter about 2 cm is pulled through muscles 52 around a vertebra 51. A miniature camera 53 is put on the sleeve 5. Vision is projected on a display screen (not shown). Tools 55 are provided on the sleeve 5 for performing the operation. The operation makes small incisions and damages minimum tissues, and thus overcoming the shortcomings above.
However, as for minimally invasive operations, when the sleeve 5 extends through the muscles 52 around the vertebra 51 and reaches a predetermined location, an end of the sleeve 5 is bound by the profile of the vertebra 51. During operation, only a vision within the sleeve 5 of about 2 cm is provided. Moreover, tools 55 are extended through the sleeve 5, and accordingly form some dead angles of vision. Thus nerves can not be abirritated enough, and thus such an operation is difficult to perform.